Biquinary glow-discharge digit indicator tube



y 1966 s. M. FROUWS ETAL 3,250,938

BIQUINARY GLOW-DISCHARGE DIGIT INDICATOR TUBE Filed May 2, 1962 INVENTOR SIMON M. F ROUWS ADRIANUS A. M. HE NDRIKS k AGE T 5427;515:354fall/15471151111/1/155157/71/5414!41156311511141!in fl FIGJ United States Patent 3,250,938 BIQUINARY GLOW-DISCHARGE DIGIT INDICATOR TUBE Simon Mari Frouws and Adrianus Anthonius Maria Hendriks, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed May 2, 1962, Ser. No. 191,874 Claims priority, application Netherlands, Jan. 31, 1962,

274,223 Claims. (Cl. 313-1095) Our invention relates to a glow-discharge indicator tube, and more particularly to a glow-discharge tube in which two groups of five cathode electrodes each having the shape of a character corresponding to a digit which are separated by a partition. One cathode of each group is connected with one cathode of the other group and a separate anode is provided for each group. Such a tube will hereinafter be referred to as a biquinary glowdischarge tube, or simply as a biquinary tube.

Customarily, in biquinary tubes, the cathodes are arranged parallel to the base of the tube. The cathodes are surrounded by a cylindrical screen, which may be connected to a partition separating the two cathode groups while two anodes are positioned adjacent the partition between the cathode groups. The partition may be left floating, or it may have applied to it approximately'half the anode voltage.

For the reproduction of a given digit a cathode voltage is applied to a pair of cathodes one of which corresponds to the digit and the associated anode has applied to it the anode voltage. The other anode has applied it approximately half the anode voltage. Since all pairs of cathodes corresponding to digits have half the anode voltage via resistors, the other cathodes remain at this voltage.

In such tubes there is the problem that the cathode connected to the cathode corresponding to the desired digit in the other tube half is likely to burn simultaneously, since the anode of the desired digit produces a discharge even across the partition.

In such tubes also the gas filling consists of a single rare gas or of a mixture of rare gases, since the addition of mercury would involve the phenomenon of too early simultaneously burning. However, since the presence of mercury strongly reduces cathode sputtering, the addition of mercury is highly desirable in order that the life of the tube may be increased.

Simultaneous burning of the interconnected cathode must be prevented, not only with the minimum current required to cover each digit, but also with a current amounting, for example, to twice that minimum, since otherwise an inadequate margin is left in the arrangement for the series resistors and the voltages applied.

It is a principal object of our invention to provide a new and novel biquinary glow-discharge indicator tube in which simultaneous burning of two digits is prevented.

A further object of our invention is to provide a new and novel biquinary glow-discharge indicator tube having a longer life.

A still further object of our invention is to provide a new and novel biquinary glow-discharge indicator tube in which cathode sputtering is reduced.

Another object of our invention is to provide a new and novel biquinary glow-discharge indicator tube containing a supply of mercury for reducing cathode sputtering and in which simultaneous burning of interconnected cathodes is prevented.

These and further objects of our invention will appear as the specification progresses.

In a biquinary glow-discharge indicator tube in which Patented May to, 1966 "ice two groups of five character-shaped cathodes, each corresponding to a digit, are separated by a partition, the cathode digits are located, in accordance with our invention, parallel to the axis of the tube. A partition extends into the proximity of the tube envelope, and insulating plates are arranged, on the upper side and on the lower side of the partition, at right angles to the axis of the tube. These plates also extend to within the proximity of the tube envelope so that for each of the cathode digit groups a separate compartment is formed.

An anode is located on the side of. each group remote from the partition, the latter being provided with openings providing a transparency of at least The smallest transverse dimension of these openings is at the most of 'the height of the cathodes. The tube also contains, in addition, a quantity of liquid mercury.

Since the tube is divided into two compartments by the partition and the insulating plates extending into the proximity of the tube envelope, the discharge cannot pass around the partition. The size of the openings in the partition, however, determines the possibility of diffusion of charges across the partition. The smallest transverse dimension, i.e., the distance between parallel wires or the transverse dimensions of square or hexagonal etched holes, is related to the height of the cathodes, since with a practical tube the height of the cathodes determines the depth of the cathode stack and hence, the relative distances available between the electrodes. Since the anodes are located on the outer side of the cathode stack, the tendency of the field of the anodes to penetrate through the partition is restricted as far as possible, so that the addition of mercury to reduce cathode sputtering and increases life is permitted, and the transparency of the partition can reach the said high value.

In a particular embodiment the anodes are provided with extensions reaching closely up to each cathode, so that for all cathodes the ignition conditions are substantially equal. These extensions may be formed by one or more pins arranged at right angles to the planes of the anodes, or by wings on the anodes laterally surrounding the cathodes and terminating substantially in the plane going through the cathode nearest the partition. In this case it is desirable for these wings to terminate opposite the closed sides of the partition.

In a tube according to the invention the rare gas pressure is at least 70 mms. Hg and the product of this pressure, in millimetres, with the distance in millimetres 1 between succeeding cathodes is at least 40. The high pressure permits, in the first place, reduction of the depth of the cathode stack. Moreover, owing to the high pressure the thickness of the cathode glow is small.

Due to the small thickness of the cathode glow, its spreading over the cathodes is hindered to a lesser extent by the adjacent cathodes at half the anode voltage than would be the case with lower pressure, while the increase of the minimum covering current in excess of the value determined by the higher current density with the higher pressure is restricted as far as possible. This favorably affects the relationship between the minimum covering current and the current at which the coupled cathode starts burning simultaneously.

In a further embodiment of the invention the distance of the cathode nearest the partition from this partition is twice the distance between succeeding cathodes, so that the tendency toward simultaneous burning is restricted. I

In accordance with the invention it is furthermore advantageous to arrange the partition between. the two cathode groups eccentrically in the tube, viewed in a cross section, i.e. towards the side of the cathode group corresponding to odd-numbered digits lying on'the front side. The disposition of the odd-numbered digits has the advantage of better visibility, while owing to the eccentric arrangement in the front part of the tube the parallax-free observation of the digits is improved. Moreover, irregularities in the tube wall are less troublesome. This arrangement, in conjunction with the arrangement of the cathodes parallel to the axis of the tube ailords the possibility of reducing, with the same size of the cathodes, the axial distances between the cathodes of tubes arranged side by side, so that reading a number of more than one digit is easier. Thus, the number appears as such, and not in the form of separate digits.

In accordance with the invention it is particularly advantageous to provide the clear envelope on the outer side with a red-colored lacquer layer, which renders invisible not only the blue haze around the cathode glow, but also the blue light spots also due to the presence of mercury, and likely to occur at random in the partition, in the case of high current intensity. With decimal digit tubes the last-mentioned phenomenon does not occur, since no partition is provided between the digits in this case.

The invention will now be described with reference to the accompanying drawing in which:

FIG. 1 is a perspective view of a biquinary tube according to the invention;

FIG. 2 is a longitudinal sectional view showing the relative arrangement of a few parts; and

FIG. 3 is a sectional view of a connecting wire and a contact pin.

Referring to FIG. 1, the electrodes of a biquinary 'tube are enclosed in a circular cylindrical envelope 1 of clear glass, having a bottom 2, comprising a plurality of contact pins 4, and an upper side 3. The electrodes are disposed between two mica plates 5 and 6, the latter being provided with resilient teeth. Mica plates 5, 6 have a diametrical slot 7 and 8 respectively to allow the supply wires and connecting wires to pass, which slots divide the mica plates almost in two pieces. The foremost anode 9 consists of gauze, having narrow beams on the upper side and on the bottom side, and side wings which reach into the plane of the digit nearest the partition. The rear anode 10 consists of iron with an iluminum coating, having a dull surface so that reflections are reduced as far as possible. A molybdenum partition 11 is arranged in front of the axis of the tube and is formed by lower and upper beams 12 and 13, respectively, and side beams 14, on which tungsten wires 15 are wound, which wires have a thickness of 10 1 and a pitch of 50 Through the upper side and the lower side of the two anodes enamelled pins 16 extend, the ends of which are provided with flattened caps 17, which are insulated from the anodes by mica plates 18. Cathode digits, having a thickness of 0.15 mm. and insulated from each other by glass beads 19 of a thickness of 0.6 mm., are strung into pins 16. On each side of the partition the cathode digits are insulated by two similar beads 19. The contact pins 4 of the tube bottom are partly connected directly to the anodes and the partition and, moreover by flexible supply wires 20 to cathode digits of the two groups, so that only one digit of each pair is connected to a pin. Connecting wires 21 extend through the slot 8 in the topmost mica plate, which connect the cathode digits of a pair with each other. The connecting wires 21, the supply wires 20 and the uncovered parts of the supply pins 4 are coated with a graphite layer 22, which prevents the wires and the pins from glowing together with the cathode digits.

A small, sealed glass tube 24, filled with a quantity of mercury 25 and surrounded by a filament wire 26 is disposed beneath mica plate 5. At a suitable time during the manufacture of the tube the mercury is released by heating the wire 26. The tube is filled with neon and an addition of 0.25% of argon, at a pressure of 100 mms. Hg.

FIG. 3 shows the graphite layer 22 for connecting wire 21 and pin 4.

The doubled cathode digit 1 and the graphite layer are the subject matter of copending patent applications Serial Nos. 191,824, now abandoned, and 191,825, filed concurrently.

While we have described our invention in connection with a specific embodiment, modifications thereof will be apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What we claim is:

1. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of spaced character-like electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartrnent for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, said partition having openings constituting at least of the partition, each of said openings having a smallest dimension which is not more than & of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope.

2. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of spaced character-like electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, each of said anodes having portions extending into close proximity to each electrode in the associated group whereby each electrode in the group ignites under substantially the same conditions, said partition having openings constituting at least 75 of the partition, each of said openings having a smallest dimension which is not more than of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition and a quantity of liquid mercury Within said envelope.

3. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of spaced character-like electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack.

- by a partition, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodesin the stack, a separate electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition disposed eccentrically relative to anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, each of said anodes having wing portions which laterally surround each of the electrodes in the'associated stack and extend into the plane of the electrode nearest the partition, said partition having openings constituting at least 75% of the partition, each of said openings having a smallest dimension which is not more than 1 of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope;

4, A glow-discharge indicator tube comprising an envelope having a given axis and containing an. ionizable gaseous medium at a pressure of about 70 mm. Hg, a plurality of spaced character-like electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, said partition having openings-constituting at least 75% of the partition, each of said openings having a smallest dimension which is not more than 4 of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope, the product of the gas pressure and the distance between successive electrodes in millimeters being at least approximately 40.

5. A glow-discharge indicatortube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of spaced character-like electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said 7 groups being separated from another group in thestack by a partition, the electrode nearest said partition being spaced therefrom a distance which is twice the distance between successive electrodes in the group, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, said partition having openings constituting at least 75% of the partition, each of said openings having a smallest dimension which is not more than of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within ,said envelope.

6. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of spaced character-like one of the two groups of electrodes separated thereby, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side 'of the group of electrodes remote from the separating partition, said partition having openings constituting at least 75 of the partition, each of said openings having a smallest dimension which is not more than & of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope.

7. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, said envelope having an outer red transparent coating for substantially eliminating the blue haze of cathode glow, a plurality of spaced characterlikeelectrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition, said electrodes being further arranged to be parallel to said given axis, said electrodes being connected in pairs one from each group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, said partition having openings constituting at least 75 of the partition, each of said openings having a smallest dimension which is not more than of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope.

8. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of character-like electrodes each shaped in the form of a digit arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition, said electrodes being further arranged to be parallel to said given axis, one electrode of each group being connected to one electrode of another group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, said partition having openings constituting at least 75% of the partition, each of said openings having a smallest dimension which is not more than of the height of one of said electrodes in said stack whereby with a potential applied toa pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope.

9. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, a plurality of spaced character-like electrodes arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition disposed eccentrically relative to one of the two groups of electrodes separated thereby, saidv electrodes being further arranged to be parallel to said given axis, one electrode of each group being connected to one electrode of another group, insulating plates arranged at either end of the stack perpendicular to said given axis and extending in close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, each of said anodes having portions extending into close proximity to each electrode in the associated group whereby each electrode in the group ignites under substantially the same conditions, said partition having openings constituting at least 75% of the partition, each of said openings having a smallest dimension which is not more than of the height of one of said electrodes in said stack whereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition and a quantity of liquid mercury Within said envelope.

10. A glow-discharge indicator tube comprising an envelope having a given axis and containing an ionizable gaseous medium, said envelope having an outer' red transparent coating for substantially eliminating the blue haze of cathode glow, a plurality of spaced characterlike electrodes each having the shape of a digit arranged in a stack, said electrodes being further arranged in groups of five within said stack, each of said groups being separated from another group in the stack by a partition disposed eccentrically relative to one of the two groups of electrodes separated thereby, said electrodes being further arranged to be parallel to said given axis, one of the electrodes of each group being connected to one electrode of another group, insulating plates arranged at either end of the stack perpendicular to said given axis and extendingin close proximity to the envelope thereby forming with the partition a compartment for each group of electrodes in the stack, a separate anode for each group of electrodes on the side of the group of electrodes remote from the separating partition, each of said anodes having portions extending into close proximity to each electrode in the associated group whereby each electrode in the group ignites under substantially the same conditions, said partition having openings constituting at least 75% of the partition, each of said openings having a smallest dimension which is not more than 4 of the height of one of said electrodes in said stackwhereby with a potential applied to a pair of interconnected electrodes only one of said electrodes glows and the glow is prevented from spreading by said partition, and a quantity of liquid mercury within said envelope.

References Cited by the Examiner UNITED STATES PATENTS 2,618,760 11/1952 Hancock et al. 313-1095 2,906,906 9/1959 McCauley et al. 3l3--109.S X -2,991,387 7/1961 McCauley 3l3l09.5 X 2,991,388 7/1961 Wightman 313109.5 3,042,826 7/ 1962 McCauley et al. 313-1095 GEORGE N. WESTBY, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner. 

10. A GLOW-DISCHARGE INDICATOR TUBE COMPRISING AN ENVELOPE HAVING A GIVEN AXIS AND CONTAINING AN IONIZABLE GASEOUS MEDIUM, SAID ENVELOPE HAVING AN OUTER RED TRANSPARENT COATING FOR SUBSTANTIALLY ELIMINATING THE BLUE HAZE OF CATHODE GLOW, A PLURALITY OF SPACED CHARACTERLIKE ELECTRODES EACH HAVING THE SHAPE OF A DIGIT ARRANGED IN A STACK, SAID ELECTRODES BEING FURTHER ARRANGED IN GROUPS OF FIVE WITHIN SAID STACK, EACH OF SAID GROUPS BEING SEPARATED FROM ANOTHER GROUP IN THE STACK BY A PARTITION DISPOSED ECCENTRICALLY RELATIVE TO ONE OF THE TWO GROUPS OF ELECTRODES SEPARATE THEREBY, SAID ELECTRODES BEING FURTHER ARRANGED TO BE PARALLEL TO SAID GIVEN AXIS, ONE OF THE ELECTRODES OF EACH GROUP BEING CONNECTED TO ONE ELECTRODE OF ANOTHER GROUP, INSULATING PLATES ARRANGED AT EITHER END OF THE STACK PERPENDICULAR TO SAID GIVEN AXIS AND EXTENDING IN CLOSED PROXIMITY TO THE ENVELOPE THEREBY FORMING WITH THE PARTITION OF COMPARTMENT FOR EACH GROUP OF ELECTRODES IN THE STACK, A SEPARATE ANODE FOR EACH GROUP OF ELECTRODES ON THE SIDE OF THE GROUP OF ELECTRODES REMOTE FROM THE SEPARATING PARTITION, EACH OF SAID ANODES HAVING PORTIONS EXTENDING INTO CLOSE PROXIMITY TO EACH ELECTRODE IN THE ASSOCIATED GROUP WHEREBY EACH ELECTRODE IN THE GROUP IGNITES UNDER SUBSTANTIALLY THE SAME CONDITIONS, SAID PARTITION HAVING OPENINGS CONSTITUTING AT LEAST 75% OF THE PARTITION, EACH OF SAID OPENINGS HAVING A SMALLEST DIMENSION WHICH IS NOT MORE THAN 1/80 OF THE HEIGHT OF ONE OF SAID ELECTRODES IN SAID STACK WHEREBY WITH A POTENTIAL APPLIED TO A PAIR OF INTERCONNECTED ELECTRODES ONLY ONE OF SAID ELECTEODES GLOWS AND THE GLOW IS PREVENTED FROM SPREADING BY SAID PARTITION, AND A QUANTITY OF LIQUID MERCURY WITHIN SAID ENVELOPE. 